1. Field of the Invention
The general field of the present invention is concerned with closure fasteners of the type commonly known as latch assemblies wherein the latch, possessing an angled face with respect to the catch disposed within the jamb is normally biased into an extended position whereby fastening of the closure is effected when closure and jamb are fully aligned. More particularly, the field of the present invention relates to such door latches operated by longitudinal displacement of a spindle having a knob attached to either end and specifically to those utilizing a cam possessing a formed aperture engaging a helically formed portion of the spindle which, by rotation in reaction to said longitudinal displacement of said spindle causes lateral displacement of the rollback thereby effecting retraction of the latch.
2. General Background of the Invention
Latch assemblies, such as those typically employed for the fastening of a common door, are characterized by a sliding latch possessing an extended face angled with respect to a catch disposed in a jamb whereby contact between the two retracts the latch, as commonly effected in closing a door, the latch extending into a cavity of the catch when fully aligned with the jamb. Such devices are further typically characterized by biasing of said latch by means of a spring; leaf, coil or other type into the extended position and possess mechanical means for retraction of said latch typically including a rollback, a spindle and a handle. Torque is exerted upon said spindle by rotational displacement of said handle thereby effecting rotation of said rollback which translates said torque into a lateral displacement, normal to said spindle, of said latch in an inward direction thereby retracting the latch and unfastening the closure.
Fundamentally, such latch assemblies enable retraction of the latch in a linear displacement which is perpendicular to a spindle to the end of which a knob or handle is attached to facilitate the application of torque upon the spindle. The application of torque hence requires exertion of force in a direction within a plane parallel to the closure. In the case of a door, it is usually desired to unfasten the closure in order to pass through a doorway. If one's hands are otherwise occupied carrying something bulky, one or more containers, or when carrying a plurality of loose objects, such as groceries for example, it is often inconvenient if not impractical for one to free a hand in order to turn the door knob as described above as required to egress through the doorway.
Therefore it is considered desirable to effect retraction of a latch of the type commonly employed to fasten doors or other closures with exertion of a force in a direction consistent with the general movement through the doorway which is normal to the face of the closure. In closures disposed to open in one direction, either inward or outward with respect to the orientation of the enclosure concerned, it is desirable to open a door either by pushing (exertion of compressive force in a direction substantially normal to the face of the closure) if the door opens outward, or by pulling (exertion of tensile force in said direction substantially normal to the face of the closure) if the door opens inward. Either action enables both unfastening and opening of the closure with a simple force applied in one direction, ie. operation with a single motion, which is recognized as inherently easier than any requiring more than a single motion such as that required by closures having a conventional latch assembly requiring rotation of the spindle prior to displacement of the closure itself.